Between 1997 and 2012, just 1.5 million doses of cholera vaccines were used worldwide. In 2017 almost 11 million were used, from Sierra Leone to Bangladesh. So far in 2018, over 15 million doses have been approved

But by far the worst-affected countries have been Somalia and South Sudan. Zambia, lies in the middle of a range of countries caught in the surge of cases, from struggling Mozambique to relatively prosperous Kenya.